B1 - Keeping Healthy

A healthy diet contains the correct amounts of carbohydrates; proteins; fats; vitamins and minerals; fibre and water. Carbohydrates, proteins and fats are used to release energy. A deficiency in any of these results in malnutrition. 

How much energy do you need?

Food supplies energy to the muscles as they work. This means that the amount of exercise you do affects the amount of energy you need. Additionally, the temperature of your surroundings affects how much energy you need. In colder climates you need to eat more food as you are using more energy to keep your body temperature at a steady rate. 

The metabolic rate

This is the speed at which chemical reactions take place in cells. This rate differs from person to person, for a number of reasons, e.g. the proportion of muscle to fat in your body. More exercise builds up more muscle and so the rate is faster. However, the basic metabolic rate is based on genetic factors you inherit from your parents. 

When more energy is taken in than required, the excess is stored as fat. Some fat is required to cushion internal organs and act as an energy store. However, too much fat leads to obesity. 

Obesity can cause health problems such as arthritis, type 2 diabetes, high blood pressure and heart disease. 

To reduce the amount of energy you take in, cut down on the foods you eat and to do more exercise. This will reduce your overall body mass. 

However, a lack of food results in deficiency diseases as a result of mineral ions and vitamins. 

The term 'malnourised' refers people who do not have a balanced diet. 

Inherited factors from your parents affect your appearance (e.g. the colour of your eyes, your metabolic rate)

Controlling cholesterol

Your body's ability to control cholesterol levels is inherited. Cholesterol is required for cell membranes and to make hormones. LDL (low-density lipoprotein) cholesterol is "bad", HDL (high-density lipoprotein) cholesterol is "good".

LDL carries cholesterol from the liver to the cells, and can cause harmful build-up. HDL cholesterol transports cholesterol from the cells to the liver, where it can be broken down. Too much cholesterol can lead to heart disease. 

Cholesterol levels can be affected by exercise. Regular exercise lowers blood cholesterol levels and helps the balance of cholesterol. 

An infectious diesease is the reuslt of a pathogen (a type of microorganism) entering and attacking the body. Common pathogens are bacteria and viruses. 

Bacteria - single-celled living organisms that are much smaller than animal or plant cells. Some can be useful for making food like yoghurt or cheese, or making medicines. 

Viruses - even smaller than bacteria. They can cause disease in any living organism. 

How pathogens can cause disease

Bacteria split in two and often produce poisons called toxins that affect the body and can directly damage cells. 

Viruses damage or destroy the cells of the body, and rarely produce toxins. 

Common disease symptoms - high temperature, headaches and rashes. 

An infectious disease is caught by picking up a pathogen from somebody else who is infected with the disease. 

Pathogens can spread from person to person in the following ways:

Droplet infection - e.g. coughing and sneezing; expelling tiny droplets from your respiratory system. Other people then breate the droplets in and so pick up the pathogens, such as the common cold. 

Direct contact - e.g. STDs or impetigo; spread by direct contact of the skin. 

Contaminated food/drink - e.g. salmonella; eating raw or undercooked foor and so pathogens are injested directly into your gut.

Through a break in the skin - e.g. HIV/Aids; pathogens can enter through scratches or cuts. 

Microbes can be prevented by the skin, which acts as the barrier or the first line of defense. It prevents the bacteria from reaching the tissues beneath that could potentially be infected. If the skin is cut, blood clots turn into scabs which forms seals over the cut and so stopping pathogens entering the wound. 

Additionally, the breathing system produces mucus which lines your lungs and tubes. The mucus traps the pathogens and is then moved out of your body or swallowed into the gut. The acid in the stomach then destroys the pathogens. 

White blood cells - the second line of defence. These defend against pathogens in three ways:

1. Ingesting the microorganism - this destroys the pathogen and stops you getting ill. 

2. Producing antibodies - Antibodies target particular bacteria and viruses and destroy them. Each pathogen needs a unique antibody. Once your white blood cells have produced antibodies against a particular pathogen, they can be made very quickly if that pathogen gets into the body again. 

3. Producing antitoxins - Antitoxins counteract the toxins produced by pathogens. 

Drugs such as aspirin or paracetamol do not have any effect on the viruses inside your body. However, they act as painkillers and relieve the symptoms of disease. 

Antibiotics are medicines that work inside the body to kill harmful bacteria. They damage the bacterial cells without having an impact on your own cells. 

However, antibiotics are not useful on infectious disease. They cannot destroy viruses because viruses reproduce inside the cells. It is difficult to develop drugs that have the ability to destroy viruses without damaging body cells. 

Microorganisms must be cultured (meaning to grow many of them at a time) so we can find out more about them. 

An uncontaminated culture of microorganisms can be grown using sterilised Petri dishes and agar. (Sterilisation means heating apparatus to kill bacteria in them prior to use). The culture is left in a sealed Petri dish at 25 degrees C for a few days. 

Uncontaminated cultures are needed so we can investigate the effect of chemicals like disinfectants and antibiotics on microorganisms. 

Cultures should be incubated at a maximum temperature of 25 degrees to reduce the likelihood of harmful pathogens growing. 

Some bacteria develop resistance to antibiotics. This change in the genetic material is called mutation. These new strains of bacteria are unaffected by the antibiotic and happen by chance as a result of natural selection. To prevent this from happening increasingly, antibiotics should be used sparingly. 

Mutation and pandemics

Another problem with mutation is that the new strains of diseases can spread very quickly, causing widespread illness because of a lack of immunity and effective treatment. The flu viruses is an example of this. Existing vaccines are ineffective against new strains of this virus. 

There be be an epidemic of disease in one country, or a pandemic across several countries. 

Every cell has unique proteins called antigens. White blood cells make antibodies which combine with the antigens to destroy the pathogens. 

Your white blood cells 'remember' which antibody tackles each pathogen, and so when they come into contact with that pathogen again, they can make the same antibody very quickly. This makes you immune to that disease. 

Vaccination

A vaccination immunises you against both viral and bacterial pathogens in the following way:

1. Small amounts of dead or inactive pathogen are injected into you. 

2. This triggers your body's natural response to invading pathogens. The antigens in the vaccine stimulate your white blood cells into making antibodies. The antibodies detroy the antigens without risk of you getting that disease. 

3. You are immune to future infections by that pathogen as your white blood cells 'remember' and can make the correct antibody once more.